The general premise of patents and copyrights is that you're going to do some development work and then you get an exclusive right that yields a competitive advantage.
Standards are different. The purpose of the standard is that Alice wants her output device to be compatible with everyone else's input device and Bob wants his input device to be compatible with everyone else's output device.
There is no competitive advantage to be had because the very premise is that everyone possible is going to implement it to maximize the network effect. And the entire industry has the incentive to want the standard to be good and put whatever good ideas they have into it because they're all stuck with it if it isn't. Meanwhile because of the network effect, everyone has to implement the standard because if they come up with their own thing -- even if it's better -- it wouldn't be compatible.
So all of the normal incentives from copyrights and patents are wrong. You can't gain a competitive advantage from it, companies have a preexisting incentive to make it good even without an exclusive right, and someone who doesn't want to pay doesn't have the option to try to do better on their own because of the network effect. And the network effect makes it an antitrust concern.
The result is that NDAs and royalties on standards are just a shakedown and the law shouldn't allow them.